GJB2 and Hearing impairment: Haung et al. reported a case who had double bi-allelic mutations in GJB2 and SLC26A4 from among 5964 Chinese hearing-impairment patients [13] and 6 cases who had co-existing mutations in GJB2 or SLC26A4 and a mitochondrial gene from among 5934 hearing-impairment Chinese patients (0.10%, 6/5934) [14].